hey man.. ya if your doing the oils then just use the good ones, there should be a recomended oil at the owners manual.
For mine, I'm using 10w60 which what the e46 m3 and the M5 uses.
- Look for cracks on the subframe of course
- Check the 5th gear issue - when you put the shifter to 5th gear and release it by tapping it slowly see if it sticks at the 5th gear gate. Common on e36's. Usually dealer will replace the tranny if on warranty. Do it when Cold
- Check for oil leaks
- Check for RSM see if its has metal sound when going over small bumps
- Check if all the instruments are working.. some may have gas gauge problems
- Check if all instrument lights are ok. Mine had a burnt out bulb on the temperature gauge.
Other than that the e36 M engines are pretty reliable and solid.